brcmfmac: remove obsolete variable from brcmf_cfg80211_start_ap()

The function brcmf_cfg80211_start_ap() had some variables declared
that were not used or not needed any longer. This patch removes
those variables.

Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Reviewed-by: Hante Meuleman <meuleman@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Franky Lin <frankyl@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>